Backing pad for sanding or polishing machines



0d. 15, 1940. Q BURLEIGH 2,217,791

BACKING PAD FOR SANDING OR POLISHING IIACHINES I Filed Nov. 4, 193a Fig.1. I

lnvehTor. ArThurQBurleig Patented Oct. 15, 1940 UNITED STATES BACKING PAD FOR SANDING OR POLISHING MACHINES Arthur C. Burleigh, .Wellesley, Mass. Application November 4, 1938, Serial No. 238,709

1 Claim.

This invention relates to backing pads for the sanding disks used on sanding or polishing machines, and particularly to backing pads which are made to flex more or less to enable the sanding disk to more readily follow the contour of curved surfaces.

One object of the invention is to provide a backing pad of this type which is so constructed that it will maintain its proper shape when the disk is being rapidly rotated.

Flexible backing pads for sanding disks are commonly made with a thickened central portion provided with means for attaching the pad to the driving shaft, and the flexibility of the pad is secured by making the portion beyond the central portion of a progressively decreasing thickness, the pad being thinnest at its periphery.

When a pad having this shape and construction is rapidly rotated, the peripheral edge of the pad tends to curl backwardly and to assume a position in or close to a plane corresponding to the plane passing through the center of gravity of the pad. This curling backwardly of the peripheral edge of the pad gives the surface of 5 the pad a rounding instead of a flat shape which is desirable in sanding flatplane surfaces.

In order to overcome this difiiculty and to produce a flexible backing pad which will hold its shape when the pad is rapidly rotating, I propose to make the pad with a thickened peripheral edge thereby placing added weight ormass at such peripheral edge. I have found that in a pad having this construction, the additional weight or mass at the peripheral edge will hold said edge in its proper shape when the pad is rapidly rotated and will prevent the periphery of the pad from bending backwardly due to the rapid rotation.

The desired flexibility of the pad is secured by making the portion of the pad between the thickened peripheral edge and the thickened central portion relatively thin, thereby providing a flexible annular zone which permits the pad to flex when it is being used for sanding rounded surfaces.

In order to give an understanding of my invention I have illustrated in the drawing a selected embodiment thereof which will'now be described after which the novel features will be pointed out in the appended claim.

In the drawing:

Fig. 1 is a sectional view through a pad embodying my invention, taken on Fig. 2; Fig. 2 is a plan view of Fig. 1.

the line l-l,

In the drawing, l indicates a backing pad for a sanding disk and 2 indicates the sanding disk of sand paper, emery cloth, or similar abrasive material which is secured to the face 3 of the backing I. The backing pad I may be made of 5 such material as flexible backing pads are usually made of, one common material being rubber re-inforced with fabric.

The flexible backing pad I is formed with the thickened central portion dto which is secured 10 a hub 5 by which the padis attached to the operating shaft 6. This hub may be secured to the pad in any suitable or usual way, one familiar way being to embed nuts 26 in the central portion of the pad and to fasten the hub to the pad 15 by means of screws 1 which extend through the flange 8 of the huband screw into the nuts. These nuts are shown as projecting slightly beyond the face of the pad as indicated at I0, and the projecting end ID of each nut is received in a 20 recess ll formed in the back side of the flange. Any other. suitable way of securing the pad to the hub 5 may be employed, however, without departing from the invention.

.The annular portion 2| of the flexible backing 25 pad which immediately surrounds the thickened portion 4 has a progressively decreasing thickness from the portion 4 to the circular line I2, and the peripheral portion i3 of the pad is made of increased thickness. This peripheral portion N! of 30 increased thickness may have different shapes without departing from the invention, and as herein shown, said portion has a progressively increasing thickness from the circle I to the circular line I and then a decreasing thickness from the line M to the peripheral edge of the pad. The front face 3 of, the pad is flat from the peripheral edge to a point well toward the center and the back face of the peripheral portion l3 of the pad has a rounded contour with a sharp 40 rise on the outer face I5 and a more gradual inclination on its inner face l6.

Because of the relative thinness of the pad in the annular zone indicated at l2, said pad will readily flex or bend in said zone when it is used 45 for polishing or sanding concavely curved surfaces, such zone thus constituting a flexing zone. The increased mass or weight in the peripheral portion l3 serves to hold said peripheral portion in its true position with its operative face in the 5 plane of the face 3 when the pad is rapidly rotated. In fact, experience has shown that when the pad is rapidly rotated, there is a tendency for the peripheral portion I3 of the pad to bend forwardly slightly, which is an advantage as it in- 55 sures that the peripheral portion of the pad will be active when polishing plane or flat surfaces.

A pad having this construction, therefore, is not subject to the disadvantage of having the peripheral portion of its operative face curling backwardly when the pad is rapidly rotated.

I claim:

A backing pad for sanding disks comprising a one-piece circular pad of flexible material having a front face against which the sanding disk rests and also having a thickened central portion with means for attachment of the pad to a shaft and an intermediate annular flexing zone of reduced ARTHUR C. BURLEIGH. 

